ZFS Log Device Enhancements

The logbias property – You can use
this property to provide a hint to ZFS about handling synchronous requests
for a specific dataset. If logbias is set to latency,
ZFS uses the pool's separate log devices, if any, to handle the requests at
low latency. If logbias is set to throughput,
ZFS does not use the pool's separate log devices. Instead, ZFS optimizes
synchronous operations for global pool throughput and efficient use of resources.
The default value is latency. For most configurations,
the default value is recommended. Using the logbias=throughput value
might improve performance for writing database files.

Log device removal – You can now remove a log device
from a ZFS storage pool by using the zpool remove command.
A single log device can be removed by specifying the device name. A mirrored
log device can be removed by specifying the top-level mirror for the log.
When a separate log device is removed from the system, ZIL transaction records
are written to the main pool.

Redundant top-level virtual devices
are now identified with a numeric identifier. For example, in a mirrored storage
pool of two disks, the top level virtual device is mirror-0.